Voltage regulator



July 26, 1955 B. SCHERER VOLTAGE REGULATOR Filed Oct. 4, 1954 :8 i0HIIIHHIIIIIHHI IIIIHHIHIIIHIIIIII BERNARD L. SCHERER INVENTOR ATTORNEYUnited States Patent Ofifice VOLTAGE REGULATOR Bernard L Scherer,Stamford, Conn, assignor to Sorensen & Company, Inc., Stamfnrd, Conn., acorporation of Connecticut Application October 4, 1954, Serial No.459,984

7 Claims. (Cl. 323--66) This invention relates to voltage regulators andhas particular reference to voltage regulators for alternating currentsupply lines which are responsive to changes of current as well aschanges of voltage. The invention also relates to a circuit whichcounteracts the distortion of wave form which is normally present involtage regulators of this type.

Prior art voltage regulators employing saturable reactors for thecontrol of constant voltage or constant current have always produced adistorted wave form at the output terminals. This condition is due tothe fact that a saturable reactor operates when its core is partlysaturated and hence produces a wave with a pronounced third harmonic.The present invention partly rectifies this disadvantage by applying adistorted wave in series with the output terminals, this wave containinga third harmonic which is 180 degrees out of phase with the harmonicproduced by the series connected saturable reactor. This circuitcorrects the wave form and at the same time helps the regulation bycontrolling the current to the load circuit in response to a sensingdevice which varies in accordance with the current flowing in the load.

One of the objects of this invention is to provide an improved voltageregulator which avoids one or more of the disadvantages and limitationsof prior art arrangements.

Another object of the invention is to regulate an alternating currentsupply and produce constant voltage with minimum wave form distortion.

Another object of the invention is to provide a voltage regulator whichis controlled by both the voltage across the load and the currentthrough it.

Another object of the invention is to provide a voltage regulator with agreater range than the usual type of alternating current regulatorcircuit.

One feature of the invention includes a voltage sensing circuit which isresponsive to the voltage across the load and which controls a saturablereactor connected to a current transformer in series with thealternating current supply.

Another feature of the invention includes a sensing device which isresponsive to the current flowing in the load circuit and produces achange in reactance which is connected in series with the alternatingcurrent supply. The combination of these two features produces an outputvoltage which is constant in voltage and is undistorted in wave form.

For a better understanding of the present invention, together with otherand further objects thereof, reference is made to the description takenin connection with the accompanying drawing.

The drawing is a schematic diagram of connections of the voltageregulator.

Referring now to the drawing the voltage regulator in cludes a pair ofinput terminals 10, 11, which are to be connected to an alternatingcurrent supply system which may vary considerably in voltage. Theterminals are connected to an autotransformer 12 which provides anFatentecl duly 28, 1955 increase in voltage and permits a voltage tapfor use by the current regulating system. Also connected to the supplyterminals 10, 11, are two transformers 13 and 14 which are coupled torectifier tubes 15' and 16 to provide high voltage direct current forthe use of two amplifying circuits which will be described later.

Input terminal 11 is connected directly to output terminal 17. The highvoltage terminal of the autotransformer 12 is connected in series withthree windings l8, 2%), and 21; the first of these 18 is the secondarywinding of a transformer whose primary winding 22 is connected inparallel with a saturable reactor winding 23. The reactance of winding23 is controlled by the direct current in winding 24 which is connectedto the output circuit of an amplifying system. Winding is a reactor on asaturable core, the reactance of which is controlled by the directcurrent in winding 25 which is derived from a second amplifying system.

Winding 21 is the primary winding of a transformer whose secondarywinding 26 is connected to the filament of a sensing diode 27 which ispart of the input circuit of the first amplifying system. One side ofwinding 21 is connected to output terminal 28, a load circuit 30 beingconnected across terminals and 17. Also connected across the outputterminals is the filament of a second diode 31 which comprises the inputcircuit of the second amplifier system.

The two amplifier systems have identical circuits hence only one will bedescribed. Diode 27 is connected as one arm of a bridge circuit, theother four arms being 32, 33, and 34. Direct current power is suppliedto conductors 35 and 36 which form opposite junction connections for thebridge system. The direct current for this bridge is supplied byrectifier 37 and the lower part of winding 38 which forms a part oftransformer 13. This direct current supply is filtered by a capacitorand a resistor 4-1.

The degree of unbalance of this bridge circuit is determined by asensing circuit which is connected to points 42 and 43, point 4-2 beingconnected in series with an anti-hunt circuit 44 and the controlelectrode of an amplifier tube 45. Point 43 is connected directly to thecontrol electrode of an amplifying tube 46. Amplifier tube 46 has itsanode connected directly to conductor 35 with its cathode connected inseries with a resistor 2-7 to conductor 36. Amplifier tube has a similarcathode connection with its anode connected to the control electrode ofan output amplifier tube The anode current for tube 45 is derived fromthe filament circuit of rectifier tube 15 in series with an inductor anda resistor 51. A voltage divider composed of resistors 49 and 52 isconnected between the positive supply line and the cathode of tube 48.The control electrode of tube 48 is connected to the junction point ofthese resistors in series with another resistor 59. The anode of tube 48is connected in series with winding 2 to the positive supply line andthe filament of rectifier tube 35.

The operation of this circuit is as follows: Variations in load currentpassing through winding 21 are transformed to a lower voltage in winding2a? which is connected directly to the filament of tube 27 in serieswith an adjustable resistor 53. These current variations change thetemperature of the filament causing it to emit a variable number ofelectrons, thereby changing the resistance between point and conductor36. These variations of resistance are applied to amplifier tube 45 andthe amplified voltage variations are applied to the control electrode oftube 48 resulting in a current through winding 24 which is controlled bythe current in windi g 21. It should be noted that the current inwinding is alternating while the current in winding is direct currentand serves only to control the reactance value of winding 23.

The distortion introduced by winding 20 is due to the partly saturatedcore which is maintained in its saturated condition by the normalcurrent through winding 25. An increase in current flow in Winding 25increases the saturation value and reduces the reactance so that a peakis added to both halves of the wave. The net result of this distortionis the creation of a third harmonic component.

The distortion introduced by winding 23 is due to the partly saturatedcore which holds windings 23 and 24. An increase in current in winding23 increases the saturation value of the core and reduces the reactancevalue of winding 23, causing it to take more than the normal value ofcurrent, thereby reducing the current through winding 22. The net resultof this distortion is the creation of a third harmonic component havinga negative maximum current value which is l80 out of phase with thenegative maximum current value of the third harmonic componentintroduced by Winding Zti. This distorted wave is applied in series withthe supply line by the unsaturated transformer 22*18 and causes thethird harmonic components to cancel each other.

The amount of third harmonic applied to winding 18 is in directproportion to the current passing through this winding. This variationis controlled by current transformer 2l26, diode 27, and the amplifyingsystem as described above.

The voltage compensating circuit which includes diode 31 and amplifiertubes 6%, 61, and 62 has been described before in patents such as No.2,682,635 issued June 29, 1954 to William H. Henrich. The output voltageis sensed by diode 31 which is part of a four-arm bridge, the otherthree arms being resistors 55, 56, and 57. This bridge is supplied witha direct current potential derived from rectifier 58 and the bridgeunbalance is sensed by tubes 66 and 61. The unbalance voltage isamplified by amplifier tube 62 and applied to winding 25 which is alsoconnected to the positive terminal of rectifier tube 16. Variations ofcurrent in winding 25 cause variations in the saturation value of thecore material and resultant variations of reactance of winding 29.

When the voltage across the load 3% increases the filament temperaturein diode 31 also increases, causing the resistance of diode 31 todecrease, thereby raising the potential on the control electrode ofamplifier tube 61. This action lowers the voltage of the anode and thecontrol electrode in amplifier tube 62, thereby lowering the anodecurrent through the tube and through winding 25 and causing an increasein the reactance value of winding 2%. potential drop across the windingand compensates for the voltage rise across the load.

From the above description it will be evident that the inventionprovides a constant alternating current voltage at a pair of loadterminals which covers a wide range of voltage values and which deliversa wave which is devoid of harmonic distortion.

While there has been described and illustrated a specific embodiment ofthe voltage regulator, it will be obvious that the amplifier circuitscould be modified and changed without departing from the field of theinvention which should be limited only by the scope of the appendedclaims.

I claim:

1. A voltage regulator for an alternating current supply systemcomprising, a coupling circuit which transfers alternating current powerfrom a pair of input terminals to a pair of output terminals connectedto a load, a first sensing system which is coupled to the outputterminals and applies an amplified direct current control signal to afirst saturable reactor connected to said This increase causes anincrease of the coupling circuit for altering the transmitted voltage,and V load, said second sensing system arranged to apply a directcurrent control signal to a second saturable reactor which is connectedin parallel arrangement with a first winding of a transformer, a secondwinding of which is in series connection between the input and outputterminals.

2. A voltage regulator for an alternating current supply systemcomprising, a coupling circuit which transfers alternating current powerfrom a pair of input terminals to a pair of output terminals connectedto a load, a first sensing system which is coupled to the outputterminals and applies an amplified direct current control signal to afirst saturable reactor connected in series between the input terminalsand the output terminals, and a second sensing system coupled in serieswith a coupling conductor which transmits a signal proportional to thecurrent taken by the load, said second sensing system connected to applya direct current control signal to a second saturable reactor which isconnected in parallel with a first winding of a transformer, a secondwinding of which is in series connection between the input and outputterminals.

3. A voltage regulator for an alternating current supply systemcomprising, a power transformer coupled to a pair of input terminals forreceiving alternating current power from a supply which may vary inapplied voltage, a coupling circuit between said transformer and a pairof output terminals connected to a load, a first sensing systemconnected to the output terminals and coupled to an amplifier whichapplies a direct current control signal to a first saturable reactorconnected in series between said transformer and one of the outputterminals, and a second sensing system coupled in series with a couplingconductor which transmits a signal proportional to the current taken bythe load, said second sensing system connected to apply a direct currentcontrol signal to a second saturable reactor which is connected inparallel with a first winding of a transformer, a second winding ofwhich is in series connection between the input and output terminals.

4. A voltage regulator for an alternating current supply systemcomprising, a power transformer coupled to a pair of input terminals forreceiving alternating current power from a supply which may vary inapplied voltage, a coupling circuit between said transformer and a pairof output terminals connected to a load, a first sensing systemconnected to the output terminals and coupled to an amplifier whichapplies a direct current control signal to a'first saturable reactorconnected in series between said transformer and one of the outputterminals, and a second sensing system coupled in series with a couplingconductor which transmits a signal proportional to the current taken bythe load, said second sensing system connected to apply a direct currentcontrol signal to a second saturable reactor which is connected inparallel with a first winding of a transformer, a second winding ofwhich is in series connection between the input and output terminals,said sensing systems each including a filamentary diode with thefilament of each diode connected to the circuit to be sensed.

5. A voltage regulator for an alternating current supply systemcomprising, a power transformer coupled to a pair of input terminals forreceiving alternating current power from a supply which may vary inapplied voltage, a coupling circuit between said transformer and a pairof output terminals connected to a load, a first sensing systemconnected to the output terminals and coupled to an amplifier whichapplies a direct current control signal to a first saturable reactorconnected in series between said transformer and one of the outputterminals, and a second sensing system coupled in series with a couplingconductor which transmits a signal proportional to the current taken bythe load, said second sensing system connected to apply a direct currentcontrol signal to a second saturable reactor which is connected inparallel with a first winding of a transformer, a second winding ofwhich is in series connection between the input and output terminals,said U first winding of the transformer also having one terminalconnected to a portion of the transformer and the other terminalconnected to a terminal of the first saturable reactor.

6. A voltage regulator for an alternating current supply systemcomprising, a power transformer coupled to a pair of input terminals forreceiving alternating current power from a supply which may vary inapplied voltage, a coupling circuit between said transformer and a pairof output terminals connected to a load, a first sensing systemconnected to the output terminals and coupled to an amplifier whichapplies a direct current control signal to a first saturable reactorconnected in series between said transformer and one of the outputterminals, and a second sensing system coupled in series with a couplingconductor which transmits a signal proportional to the current taken bythe load, said second sensing system connected to apply a direct currentcontrol signal to a second saturable reactor Which is connected inparallel with a first winding of a transformer, a second winding ofwhich is in series connection between the input and output terminals,said sensing systems each including a filamentary diode which is one armof a four arm Wheatstone bridge and having the filament of each diodecoupled to the circuit to be sensed for changes.

7. A voltage regulator for an alternating current supply systemcomprising, a power transformer coupled to a pair of input terminals forreceiving alternating current power from a supply which may vary inapplied voltage, a coupling circuit between said transformer and a pairof output terminals connected to a load, a first sensing systemconnected to the output terminals and coupled to an amplifier whichapplies a direct current control signal to a first saturable reactorconnected in series between said transformer and one of the outputterminals, a second sensing system coupled in series with a couplingconductor which transmits a signal proportional to the current taken bythe load, said second sensing system connected to apply a direct currentcontrol signal to a second saturable reactor which is connected inparallel with a first winding of a transformer, a second winding ofwhich is in series connection between the input and output terminals,and a power supply for said first winding of the transformer which isderived from the power transformer.

No references cited.

